The present invention generally relates to a method for manipulating a three-dimensional (hereinafter “3D”) image on a two-dimensional (hereinafter “2D”) touchpad. A need exists for manipulation of three-dimensional images in a variety of fields including medical imaging, artistic design, engineering design including computer aided drafting (CAD), kinesiology, sports simulation, geological research and archeology. The invention is not limited to any particular field of research or endeavor.
Interactive input systems allow users to provide input into an application program using an active pointer (e.g., a pointer that emits light, sound or other signal), a passive pointer (e.g., a finger, a cylinder, or other suitable object) or other suitable input device are known. Multi-touch interactive input systems that receive and process input from multiple pointers using machine vision are also known. More specifically, a subset of multi-touch systems use capacitive touch panels having an insulator, such as glass, and coated with a transparent conductor such as indium tin oxide (ITO) are also known. Further, it is known that the human body is an electrical conductor. Thus, a person may touch the surface of a multi-touch system screen to distort the screen's electrostatic field. The distortion may be measurable as a change in capacitance. Also, different technologies may be used to determine the location of the touch before sending the location to a controller for processing.
Projected Capacitive Touch (hereinafter “PCT”) technology is a variant of capacitive touch technology. PCT touch screens may have a matrix of rows and columns of conductive material layered upon sheets of glass. PCT touch screen fabrication techniques may include etching a single conductive layer on sheets of glass to form a grid pattern of electrodes or by etching two separate perpendicular layers of conductive material with parallel lines or tracks to form a grid. Voltage applied to this grid creates a uniform electrostatic field that can be measured. A conductive object, such as a finger, for example, may contact a PCT panel to distort the local electrostatic field at that point to thus create a measurable change in capacitance. Further, if the finger bridges the gap between two of the etched “tracks” on the glass, the charge field may be further interrupted and thus detected by a controller. Accordingly, the capacitance may be altered and measured at every individual point on the grid allowing the system to accurately track touches. Further, PCT systems may sense a passive stylus or gloved fingers as well.
Two variants of PCT technology are generally known, namely, mutual capacitance and self-capacitance. Mutual capacitance relies on conductive objects that may hold a charge when the conductive objects are placed in close proximity. In mutual capacitive sensors, a capacitor is provided at every intersection of each row and each column. A 16-by-14 array, for example, has 224 independent capacitors. The local electrostatic field created by a grid of independent capacitors may be altered by applying a voltage to the grid and/or bringing a finger or conductive stylus close to the surface of the sensor to reduce mutual capacitance. The capacitance change at every individual point on the grid is measured to accurately determine the touch location by measuring the voltage in the other axis. Mutual capacitance allows a multi-touch operation where multiple fingers, palms or styli are tracked at the same time. In comparison, currently available methods do not use mutual capacitance technology.
Self-capacitance, i.e. the amount of electrical charge that is added to an isolated conductor to raise its electrical potential by one unit, may be used in PCT technology. Self-capacitance sensors may be designed to employ the same X-Y grid as mutual capacitance sensors; however, the columns and rows in such an arrangement may operate independently. With self-capacitance, the capacitive load of a finger is measured on each column or row electrode by a current meter. This method produces a stronger signal than mutual capacitance. However, the method is unable to accurately resolve more than one finger and thus results in “ghosting”, or misplaced location sensing.
Advances in the ability to manipulate 3D objects on a screen may prove especially beneficial in medical imaging applications. The field of medical imaging includes a variety of imaging modalities including, but not limited to, magnetic resonance imaging (“MRI”), x-ray (“XR”), computed tomography (“CT”), ultrasound and positron emission tomography (“PET”). These imaging modalities may generate three-dimensional images of anatomic structures. Physicians, medical students and other healthcare professionals often manipulate these structures for analysis from various angles. In the case of 3D ultrasound, many practitioners use joysticks connected to a terminal. Further, the use of a joystick may require that the physician use a dedicated terminal. Thus, practitioners often manipulate images from a remote location either during a procedure as part of a collaborative effort and/or as part of a post-procedure analysis.
Similarly, a need exists for engineers and other professionals to examine mechanical structures from multiple angles and at various physical locations. A need also exists for artists, architects, interior decorators, graphic designers and/or other designers to view and manipulate 3D images of various products and designs.